Plasma enhanced chemical vapor deposition method of forming titanium silicide comprising layers

ABSTRACT

A first cleaning is conducted on a plasma enhanced chemical vapor deposition chamber at room ambient pressure. After the first cleaning, elemental titanium comprising layers are chemical vapor deposited on a first plurality of substrates within the chamber using at least TiCl 4 . Thereafter, titanium silicide comprising layers are plasma enhanced chemical vapor deposited on a second plurality of substrates within the chamber using at least TiCl 4  and a silane. Thereafter, a second cleaning is conducted on the chamber at ambient room pressure. In one implementation after the first cleaning, an elemental titanium comprising layer is chemical vapor deposited over internal surfaces of the chamber while no semiconductor substrate is received within the chamber. In another implementation, a titanium silicide comprising layer is chemical vapor deposited over internal surfaces of the chamber while no semiconductor substrate is received within the chamber.

TECHNICAL FIELD

This invention relates to plasma enhanced chemical vapor depositionmethods of forming titanium silicide comprising layers.

BACKGROUND OF THE INVENTION

Conductively doped silicon regions are conventionally utilized assource/drain regions of field effect transistors and as other nodelocations in integrated circuitry. In fabricating integrated circuitryhaving such regions, insulative layers are typically fabricated over theregions and contact openings are formed therethrough to the regions.Conductive material is ultimately received within the openings and makeselectrical connection with the conductively doped source/drain or otherregions. Exemplary conductive materials include conductively dopedpolysilicon and other semiconductive materials, metals, and metalcompounds.

Refractory metal silicides, such as titanium silicide, have beenutilized as part of the conductive material, typically as an interfaceregion between the conductively doped silicon region and other overlyingconductive material. One prior art method of forming the titaniumsilicide is to deposit elemental titanium and thereafter heat thesubstrate to cause a reaction of the deposited titanium with underlyingsilicon to form the silicide. Alternately, deposition conditions can beselected such that the depositing titanium reacts with the silicon fromthe substrate during deposition to form the silicide. In eitherinstance, silicon is consumed from the underlying substrate diffusionjunction region in forming the silicide.

In certain applications, particularly in light of the ever-increasingdensity of circuitry being fabricated, it is highly undesirable for asignificant quantity of the underlying silicon of the junction to beconsumed. Accordingly, methods have been developed which prevent, or atleast reduce, underlying silicon consumption by providing a siliconsource other than or in addition to the silicon of the substrate forforming the silicide. One prior art method is to plasma enhance,chemically vapor deposit the silicide by combining a silane gas andTiCl₄ under suitable reaction conditions to form titanium silicide whichdeposits over the junction region with minimal if any consumption ofsubstrate silicon. Unfortunately, the wafer surface has been found onoccasion to become contaminated with particles in processes utilizingTiCl₄ and a silane as compared to primarily forming the silicide byreacting titanium with silicon of the substrate.

It was surmised that the particles which were undesirably forming on thewafers might be occurring during either or both of the actual titaniumsilicide deposition or after the deposition when the wafers were beingmoved into and out of the reactor chamber. While unclear, it wastheorized that the particle formation might be occurring from silaneand/or chlorine constituents adhering to the chamber sidewalls perhapsas a result of the deposition, or that chlorine was somehow undesirablybeing added to the chamber walls during a chamber cleaning which useschlorine intermediate each wafer deposition.

For example, one exemplary prior art processing intending to reduceparticle count employs a Cl₂ clean between titanium silicide depositionson separate wafers. For example, after a silicide deposition on onewafer within a reactor chamber, the wafer is removed from the chamber.Then, an argon flow of 500 sccm as a purge gas is flowed through thechamber. This is followed by a Cl₂ flow of 2,000 sccm for two seconds asa stabilizing step, with the Cl₂ flow then being continued at 2,000 sccmfor an additional 15 seconds. The intended effect of the Cl₂ clean is toremove titanium material which might undesirably adhere to the internalsurfaces of the chamber during the titanium silicide deposition. Uponcompletion of the Cl₂ cleaning step, an 8,000 sccm argon purge feedingis conducted to remove the chlorine. This is followed by a flow of Ar at8,000 sccm in combination with 1,000 sccm of He. He is lighter than Ar,and can facilitate chamber purging and cleaning, and also facilitatestemperature control within the chamber. Subsequently, another wafer isprovided within the chamber, and titanium silicide deposition isconducted.

The above-described cleaning process is typically conducted between eachsingle wafer deposition, and typically in the absence of plasma. Yetevery 10 to 20 wafer depositions, the chamber is also typicallysubjected to a plasma clean with Cl₂ to better clean/remove titaniumfrom the chamber walls. Further, every 5,000 or so wafer depositions,the whole system is subjected to an atmospheric/room ambient pressurewet clean and scrub (i.e., using NH₄OH H₂O₂ and isopropyl alcohol invarious steps) whereby the whole system is cleaned out. The otherabove-described cleanings are typically conducted with the reactorchamber essentially at the deposition pressure and temperatureconditions.

The invention was principally motivated towards overcoming theabove-described surface defect issues, but is in no way so limited. Theinvention is only limited by the accompanying claims as literally wordedwithout limiting or interpretative reference to the specification, andin accordance with the doctrine of equivalents.

SUMMARY

The invention includes plasma enhanced chemical vapor deposition methodsof forming titanium silicide comprising layers. In one implementation, afirst wet cleaning is conducted on a plasma enhanced chemical vapordeposition chamber at room ambient pressure. After the first wetcleaning, elemental titanium comprising layers are chemical vapordeposited on a first plurality of substrates within the chamber using atleast TiCl₄. After depositing elemental titanium comprising layers overthe first plurality of substrates, titanium silicide comprising layersare plasma enhanced chemical vapor deposited on a second plurality ofsubstrates within the chamber using at least TiCl₄ and a silane. Afterdepositing the titanium silicide comprising layers on the secondplurality of substrates, a second wet cleaning is conducted on thechamber at ambient room pressure.

In one implementation after the first wet cleaning, an elementaltitanium comprising layer is chemical vapor deposited over internalsurfaces of the chamber while no semiconductor substrate is receivedwithin the chamber. In one implementation after the first wet cleaning,a titanium silicide comprising layer is chemical vapor deposited overinternal surfaces of the chamber while no semiconductor substrate isreceived within the chamber.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

This disclosure of the invention is submitted in furtherance of theconstitutional purposes of the U.S. Patent Laws “to promote the progressof science and useful arts”(Article 1, Section 8).

The invention encompasses plasma enhanced chemical vapor depositionmethods of forming titanium silicide comprising layers over a pluralityof substrates, such as semiconductor substrates. The description belowand concluding claims include references to first, second, etc.substrates, cleanings, etc. Such only indicate sequence with respect tothe respective acts or nouns which they qualify, and in no way precludeother processing occurring intermediate any of the stated processings,nor do they preclude processing prior to the first stated processing norafter the last stated processing, unless otherwise indicated.

In accordance with an aspect of the invention, a first cleaning isconducted in a plasma enhanced chemical vapor deposition chamber at roomambient pressure. Typically, such a cleaning would be conducted after aprevious series of depositions upon semiconductor substrates within thechamber. By way of example only, an exemplary cleaning includesproviding the reactor chamber at atmospheric pressure and internalcomponents at below 100° C. Certain components, such as the lid, arecleaned with an aqueous solution of NH₄OH and H₂O₂. Other portions ofthe chamber are cleaned with a 30% by volume H₂O₂ solution, followed bya deionized water cleaning, and then cleaning with isopropyl alcohol.The invention was reduced-to-practice in the context of utilizing aCentura Model #2658, available from Applied Materials of Santa Clara,Calif., having an internal volume of 6.55 liters. However, any reactorand any first cleaning, whether wet or dry, and whether existing oryet-to-be-developed, are contemplated.

In one implementation after the first cleaning, elemental titaniumcomprising layers are chemical vapor deposited on a first plurality ofsubstrates within the chamber using at least TiCl₄. This preferablyoccurs without any substrate depositions occurring between the firstcleaning and starting with the elemental titanium comprising layerdepositing. Such depositions can be conducted with or without plasma,with plasma deposition being preferred. Further, the layers can bedeposited to consist essentially of elemental titanium. By way ofexample only and in the above reactor chamber, exemplary depositionconditions include a substrate temperature of from 600° C. to 700° C.,pressure within the chamber at from 3 Torr to 6 Torr and applied powerof from 200 watts to 600 watts. Preferred gas flows include TiCl₄ atfrom 50 sccm to 150 sccm, argon flow at from 2,000 sccm to 6,000 sccm,He at from 1,000 sccm to 2,000 sccm and hydrogen flow at from 2,000 sccmto 10,000 sccm.

Preferably, the first plurality constitutes at least 20 substrates,preferably semiconductor substrates, yet is also preferably no greaterthan 200 substrates. In one preferred embodiment, the plurality is nogreater than 100 substrates, and in another preferred embodiment is nogreater than 50 substrates. A preferred effect in such processing is toreduce surface particle count, as will be further described below.Reduction-to-practice occurred in a single wafer plasma enhancedchemical vapor deposition reactor and in depositing a single elementaltitanium comprising layer separately on the respective substrates,although the invention is not so limited.

After depositing elemental titanium comprising layers over the firstplurality of substrates, titanium silicide comprising layers are plasmaenhanced chemical vapor deposited on a second plurality of substrateswithin the chamber using at least TiCl₄ and a silane. One or moresilanes might be utilized, with an exemplary preferred silane beingSiH₄. Silanes including more than one silicon atom, as well as organicsilanes, are also of course contemplated. Preferred processing for theabove-described titanium silicide deposition is as described above withrespect to the elemental titanium comprising layer deposition, but withthe addition of an exemplary flow of SiH₄ at 0.5 sccm to 10 sccm. Plasmageneration can be direct within the chamber, and/or remote from thechamber.

Preferably, the number in the second plurality of substrates will begreater than the first, for example by a factor of at least 5 in oneembodiment, and more preferably by at least 10. A preferred intent isthat the first plurality processing be sufficient in number to reducethe undesired surface particle count in a first-in-time deposited subsetof the second plurality of substrates than would otherwise occur underidentical processing conditions but without the chemical vapordepositing of elemental titanium on the first plurality of substrates.It was discovered that the adverse, undesired surface particle countthat was occurring in the prior processing typically would cease aftertitanium silicide depositions of a certain number, for example at agreater than 200 semiconductor wafer processings in a single waferchamber. In accordance with the above-described preferred aspect of theinvention, it was discovered that the undesired surface particle countcould be reduced significantly by depositing elemental titaniumcomprising layers, and preferably layers that consist essentially ofelemental titanium, over some first plurality of substrates prior tostarting titanium silicide layer depositions. Although not fullyunderstood, it is theorized that some form of seasoning effect occurswithin the chamber which reduces the quantity of adhering adversematerial within the chamber (meaning that which was previously producingthe high volume of surface particles) when such elemental titaniumcomprising layers deposition is first conducted. In certain instances,satisfactory results were achieved after elemental titanium layerdepositions over only 20 substrates. In other instances, reduction inundesired surface particle count was not achieved until at least 50, 100or some number between 100 and 200 substrates were processed by anelemental titanium comprising layer deposition on a first plurality ofsubstrates.

After depositing the titanium silicide comprising layers on the secondplurality of substrates, another cleaning, herein referred to forconvenience as a second cleaning, is conducted on the chamber at ambientroom pressure. Such might be the same or different from theabove-described first ambient room pressure cleaning. Typically and mostpreferably, the chamber will be provided at subatmospheric pressureafter the first stated cleaning for deposition of the elemental titaniumand titanium silicide comprising layers. In accordance with a mostpreferred aspect, the chamber will not be exposed to room ambientpressure after being provided at such sub-atmospheric pressure untilsome time after depositing the titanium silicide layers on the secondplurality of substrates, and is then exposed to such ambient roompressure preparatory to conducting the second cleaning.

The chamber can also of course be subjected to cleanings intermediatethe single wafer cleanings, and/or intermediate some group of singlewafer cleanings.

In another implementation, a first cleaning of a plasma enhancedchemical vapor deposition chamber is conducted at room ambient pressure,for example as described above. After such cleaning, an elementaltitanium comprising layer and/or a titanium silicide comprising layeris/are deposited over the internal surfaces of the chamber while nosemiconductor substrate is received within the chamber. An exemplarypreferred thickness range for such a layer or layers is from 100Angstroms to 1,000 Angstroms.

After depositing the elemental titanium comprising layer and/or titaniumsilicide comprising layer over the internal surfaces of the chamberwhile no semiconductor substrate is received therein, titanium silicidecomprising layers are plasma enhanced chemical vapor deposited on aplurality of semiconductor substrates within the chamber using at leastTiCl₄ and a silane, for example as described above. Then, at some point,the chamber is subjected to a second cleaning at ambient room pressure.

In a most preferred embodiment, elemental titanium depositing ortitanium suicide layer depositing over such internal surfaces, in theabsence of a semiconductor substrate within the chamber, is effective toreduce undesired surface particle counts in a first-in-time depositedsubset of the plurality of semiconductor substrates than would otherwiseoccur under identical processing conditions but without said elementaltitanium depositing over the internal surfaces of the chamber. It istheorized that such chamber surfacing depositing(s) has a seasoningeffect to the reactor which reduces undesired surface particle counts,particularly in a first set of wafers which are deposited using TiCl₄and a silane.

In compliance with the statute, the invention has been described inlanguage more or less specific as to structural and methodical features.It is to be understood, however, that the invention is not limited tothe specific features shown and described, since the means hereindisclosed comprise preferred forms of putting the invention into effect.The invention is, therefore, claimed in any of its forms ormodifications within the proper scope of the appended claimsappropriately interpreted in accordance with the doctrine ofequivalents.

What is claimed is:
 1. A plasma enhanced chemical vapor depositionmethod of forming titanium silicide comprising layers over a pluralityof substrates, comprising: first cleaning a plasma enhanced chemicalvapor deposition chamber at room ambient pressure; after the firstcleaning, chemical vapor depositing elemental titanium comprising layerson a first plurality of substrates within the chamber using at leastTiCl₄; after depositing elemental titanium comprising layers over thefirst plurality of substrates, plasma enhanced chemical vapor depositingtitanium silicide comprising layers on a second plurality of substrateswithin the chamber using least TiCl₄ and a silane; and after depositingthe titanium silicide comprising layers on the second plurality ofsubstrates, second cleaning the chamber at ambient room pressure.
 2. Themethod of claim 1 wherein the chemical vapor depositing of the elementaltitanium comprising layers occurs without any substrate depositionsoccurring between the first cleaning and starting of said elementaltitanium comprising layer depositing.
 3. The method of claim 1 whereinthe chemical vapor depositing of the elemental titanium comprisinglayers is conducted with plasma generation.
 4. The method of claim 1wherein the first plurality is at least 20 substrates.
 5. The method ofclaim 1 wherein the first plurality is from 100 substrates to 200substrates.
 6. The method of claim 1 wherein the first plurality from 20substrates to 100 substrates.
 7. The method of claim 1 wherein the firstplurality is from 20 substrates to 50 substrates.
 8. The method of claim1 wherein the elemental titanium comprising layers consist essentiallyof elemental titanium.
 9. The method of claim 1 wherein the chamber is asingle wafer processor, and the elemental titanium and titanium silicideare respectively deposited in a single layer on each respectivesubstrate between the first and second cleanings.
 10. The method ofclaim 1 wherein the second plurality is greater in number than the firstplurality.
 11. The method of claim 1 wherein the second plurality isgreater in number than the first plurality by a factor of at least 5.12. The method of claim 1 wherein the second plurality is greater innumber than the first plurality by a factor of at least
 10. 13. Themethod of claim 1 wherein the first plurality is sufficient in number toreduce undesired surface particle count in a first in time depositedsubset of the second plurality of substrates than would otherwise occurunder identical processing conditions but without said chemical vapordepositing of elemental titanium on the first plurality of substrates.14. The method of claim 1 further comprising providing the chamber atsubatmospheric pressure after the first cleaning, the chamber not beingexposed to room ambient pressure after being provided at thesubatmospheric pressure until some time after depositing the titaniumsilicide layers on the second plurality of substrates.
 15. The method ofclaim 1 wherein the first plurality is sufficient in number to reduceundesired surface particle count in a first in time deposited subset ofthe second plurality of substrates than would otherwise occur underidentical processing conditions but without said chemical vapordepositing of elemental titanium on the first plurality of substrates;and further comprising providing the chamber at subatmospheric pressureafter the first cleaning, the chamber not being exposed to room ambientpressure after being provided at the subatmospheric pressure until sometime after depositing the titanium silicide layers on the secondplurality of substrates.
 16. The method of claim 1 wherein the plasmadepositing of titanium silicide comprising layers occurs with plasmageneration within the chamber.
 17. The method of claim 1 wherein theplasma depositing of titanium silicide comprising layers occurs withplasma generation remote from the chamber.